A process for navigating an unmanned vehicle as well as such an unmanned vehicle is known, by way of illustration, from European Patent Document EP 0 193 985 A1. In this state of the art unmanned vehicle, and the process for navigating the same, a first sensor determines the path covered by the vehicle. The "rough" present position of the vehicle is ascertained by the output signals of the aforementioned sensor. At least one other sensor, which identifies the pattern indicated on the floor, is provided to check this position determination, whereby the determined actual/planned position of the vehicle is assigned to a specific pattern respectively.
The state of the art vehicle, and the process therefor, have a number of disadvantages.
One grave disadvantage to be pointed out is that specific patterns must be indicated on the floor of the area in which the vehicle moves. These patterns usually have to be indicated on the floor at some later date, so that the vehicle cannot be put to use with a minimum of effort in a "completely new setting". Moreover, the vehicle must "drive over" the patterns on the basis of which it checks its position. If there are relatively big deviations in position--by way of illustration when wheel slippage is too great--the vehicle does not detect a pattern at the presumed planned position and, therefore, is "helpless" in determining the position. Usually, as a consequence, the vehicle switches itself off and has to be repositioned by an operator.
Another disadvantage is that all the markings are identical. One strip or pattern cannot be distinguished from another. If a grid is not detected or if there are considerable deviations in position, errors in navigating can occur as a consequence.
There are, however, other reasons why identifying such patterns indicated on the floor may present problems: inevitably, extant dirt, etc. may cover or alter such patterns, which can be an extreme nuisance if the unmanned vehicle is employed as a cleaning vehicle, by way of illustration, shampooing the floor in one operation and giving it further treatment in another as pattern detection through the foam on the floor from the shampooing operation usually becomes impossible.
For this reason, Japanese patent applications 58-200360 and 58-201652 propose a cleaning vehicle that first gathers information on the peripheral area of the surface to be cleaned and begins a to-and-fro motion to clean the floor on the basis of this information. This occurs, by way of illustration, in such a manner that the device first drives along the entire outer region of the area and in this way stores the detected data in order to then, beginning on one side of the area, drive meanderingly to and fro within it, so that immediately adjacent, under certain circumstances, minimally overlapping strips of area can be cleaned consecutively.
This manner of navigating a cleaning vehicle often results in errors, because, due to unavoidable exterior influences, the driven wheel or wheels may demonstrate non-uniform slippage behavior caused by varying surface structure of the floor and small uncontrolled deviations from the course may occur due to ambient influences and, under certain circumstances, to powers produced by the cleaning aggregate. Thus, it can happen that the cleaning vehicle drives beyond the determined boundary of the area or does not quite reach the edge of the area and/or the parallel paths of the to-and-fro motion are not adjacent and/or parallel enough to each other to provide a continuous, cleaned surface. Moreover, the deviations from the path arising with the afore-described state of the art vehicle present a potential safety hazard to the operator.
An unmanned vehicle is also previously known (SPIE Vol. 521 Intelligent Robots and Computer Vision (1984), pp. 62-73), in which a lawnmower is equipped with a camera producing images of the surrounding area during operation. These images are digitized yielding in this manner navigational data.
A navigational system of this type is extremely complex and costly in construction and requires large storage and computation capacities. If these are not available or cannot be accommodated in a compact vehicle, by way of illustration a cleaning vehicle, the result is a very slow driving and operating speed accompanied by distinct economic disadvantages for the operator.
Furthermore, from DE 31 13 086 A1 it is known how to navigate by having the vehicle measure its distance by means of retroreflectors attached to walls of the room. However, this prior art manner of navigating has a number of disadvantages:
Firstly, it is necessary that the vehicle be built so high that it has "eye contact" with the retroreflectors attached to the walls of the factory hall over the objects in the hall. Secondly--and this is the major drawback of this state of the art navigating process--constant measuring and assessing the distance is necessary. Otherwise in a hall of regular shape, by way of illustration with a square floor plan, the measured values cannot be unequivocally assigned to the various retroreflectors attached to the walls of the hall, insofar as the vehicle cannot ascertain the distance to three walls simultaneously, which usually is, however, not possible with typical factory hall configurations.
Thus, the above described state of the art vehicle requires a great amount of computation which consequently led to the concept in this publication to leave the navigation of the vehicle to a stationary computer to which the signals from the sensors are transmitted telemetrically.